Proximity Services (ProSe) are new features of a 3GPP communications network, providing services for ProSe-enabled user equipment devices (UEs) in proximity of each other. These features are standardized in TS 22.278 v13.0.0 and TS 23.303 v13.0.0.
ProSe features consist of ProSe discovery and ProSe direct communication. ProSe discovery identifies ProSe-enabled UEs in proximity of each other. ProSe direct communication enables the establishment of communication paths between ProSe-enabled UEs in direct communication range.
One issue with the current protocol is that it may be possible for an attacker to listen on the air interface at a first location, collect discovery messages broadcast by a first UE, and broadcast the discovery messages from a second location. A second UE, in the vicinity of the second location, can be deceived into believing that it is in the vicinity of the first UE. This has been described as the spatial replay problem.